Embodiments of the disclosure relate generally to an imaging method and an imaging system, and more particularly to an imaging method and an imaging system of tube voltage and current optimization for computed tomography (CT) scans.
X-ray scans and x-ray computed tomography (CT) scans are used in a wide range of medical and industrial settings to generate images of structures within a three-dimensional subject or object that are otherwise invisible to the naked eye. For example, CT scans of medical patients are used in a wide range of pathologies including, but not limited to, identification of tumors, infectious process, infarctions, calcification, hemorrhage, and trauma. In the description that follows, the disclosed methods apply equally to scanning one of a patient and object.
While x-ray and CT scans are widely used, the x-ray radiation that is generated during the scans may increase risk of cancer for the patient being scanned. One goal is to control the exposure to radiation for humans and other living subjects that undergo the CT scan while also generating images with sufficient clarity and resolution to be useful in diagnostic procedures. This balance between the need to use the lowest x-ray radiation possible while maintaining an image quality required for optimal identification of pathology is known as ALARA “as low as reasonably achievable.” During a CT scan, an x-ray source, such as an x-ray emitting tube, rotates around the longitudinal axis of the patient while emitting x-ray radiation. Some of the x-ray energy passes through the patient to a detector on the opposite side of the patient from the x-ray emitter, while the patient absorbs a portion of the x-ray energy, known as the radiation dose. A lower-dose CT scan produces images that have a higher noise level and/or poor contrast-to-noise ratio, which can obscure detail about structures within the patient. Increasing the intensity of the x-ray exposure improves the quality of images, but the patient also absorbs additional x-ray radiation during the scan.
The amount of x-ray radiation delivered to the patient and the quality of the images are dependent on the energy fluence emitted from the x-ray source. When the x-ray tube is employed as a radiation source, the energy fluence is determined by the scanning parameters such as the tube current (mA) and the tube voltage (kV). The power output of the tube is expressed as a product of the tube current and the tube voltage. The dose that the patient receives from the CT scanner corresponds to the portion of the emitted power from the tube that is absorbed by the tissue in the body of the patient multiplied by the length of time that the patient is exposed to the x-rays from the tube. For example, higher levels of tube current and higher tube voltage generally result in a lower noise image, but deliver x-ray radiation to the patient at a correspondingly higher rate. In addition, the image quality and the dose can be different for different patients and/or applications when the power from the tube is the same. Currently, the same scan protocol and the same tube power are used to scan different patients.
It is desirable to provide a solution to address at least one of the above-mentioned problems.